The invention relates to a loose flange for connecting pipes at opposite pipe ends each provided with a collar, having an annular flange body which has a plurality of circumferentially distributed outer through-passage openings for fastening means.
The invention also relates to a method of producing a loose flange for a pipe connection, which has a plurality of circumferentially arranged outer through-passage openings.
It is known, for the sealing connection of pipes, to use annular flanges with distributed through-passage openings in the region of pipe ends. The flanges are positioned as loose flanges in each case on an encircling collar of the pipe end and braced by means of bolts, guided through the circumferentially distributed through-passage openings, in conjunction with nuts positioned at free ends of said bolts, with the result that a fixed and sealing connection is produced between the ends of the two pipes. In this case, the loose flanges each butt against a pipe end on a side of the collar of the pipe end which is directed away from the opposite pipe ends.
Since the axial bracing forces prevail in the radially outward direction from the collars, it may be the case that the loose flanges move towards one another in an outer region and are thus deformed on a permanent basis. The flanges then have an undesired thrustoconical shaping. During the bracing of such a pipeline flange connection by the tightening of the bolts, the seal and the collars are compressed, the flanges are inverted and the screws are expanded.
In particular when loose flanges are used in pipelines made of polymer material, creep of the force-carrying elements, the collars, the seal and the loose flanges in particular, cannot be avoided, with the result that the sealing forces decrease. The clamping bolts or clamping screws, with their small amount of expansion, usually cannot compensate for the creep of the polymer-material parts. Although it would be possible for axially elastic loose flanges to compensate for the creep, such a desirably pliable flange would have the basic disadvantage mentioned above that, in the case of mechanical loading, the flange, in accordance with its low axial rigidity, would deform axially to a pronounced extent and/or be inverted. The effect of the associated conical deformation of the flanges is thereby intensified, which would result in the bearing surfaces for the screws tilting and thus in the screws being subjected to undesired eccentric loading.
It is thus an object of the present invention to develop a loose flange for a pipe connection so as to ensure defined axial resilient rigidity and deformability without the screw-bearing surfaces being inclined disadvantageously and the screws being subjected to eccentric loading as a result.
In order to achieve this object, the loose flange according to the invention, in conjunction with the preamble of Patent Claim 1, is characterized in that the flange body has an inner ring section and an outer ring section, a radially inner side of the inner ring section having, at least in certain regions, a circumferentially running groove of a predetermined depth.
The particular advantage of the loose flange according to the invention is that defined axial rigidity is ensured by the provision of a groove in an inner ring section of the flange body. The groove allows specific elastic deformability of the loose flange in a radially inner region of the same. The axial rigidity of the loose flange decreases from an outer region to an inner region of the same, with the result that an additional fastening means, namely a clamping bolt with a head or a screw, is always retained with predetermined surface-area abutment against the loose flange.
It is advantageously possible to prevent undesired xe2x80x9cdishingxe2x80x9d of the flange body or tilting of the outer ring section as a result of an excessively large tightening torque. Non-uniform bearing of the ends of the fastening means, in particular of a nut and of a screw head, on radial surfaces of the flange body may thus be reliably avoided.
According to a preferred embodiment of the loose flange, the groove is of V-shaped design and runs continuously in the circumferential direction. The contour of the groove-forming oblique surfaces may be of planar or curved design here. The shape of the groove depends on the desired deformation characteristics of the inner ring section. The shape of the groove depends on the geometry of the loose flange and/or on the predetermined desired clamping force of the flange connection.
In conjunction with a radial surface for the flange parts of the flange body which is directed towards the collar, the groove is shaped such that, with the flange being subjected to nominal loading, the establishing inversion or tilting of the outer ring section is compensated for, the radial surface of the flange body butting against the collar over its surface area, with a relatively low level of surface pressure being formed in the process.
According to a development of the loose flange, circumferentially distributed and radially inwardly projecting protuberances are arranged on an inner side of the inner ring section, said protuberances retaining the loose flange with clamping action at the pipe end. It is thus possible for the loose flange to be fixed on the pipe for installation purposes.
According to a development of the loose flange, on a side located opposite the oblique surface, the flange parts have radial surfaces with a prism-like surface structure which, when clamping screws are tightened, deform and level out such that when the predetermined tightening torque of the clamping screws is reached, the washers have reached their definitive position and it is no longer possible for them to be lowered any further. It is thus possible to see when the predetermined tightening torque of each screw has been reached by the position of the respective washer. Furthermore, the visibly deformed geometry gives an indication of prior use.
According to a development of the loose flange, circumferentially distributed clamping noses are arranged on an inner side of the outer through-passage openings, with the result that clamping screws are retained with clamping action in the through-passage openings. This facilitates, in particular, the vertical installation of the flange connection. These clamping noses, and also the protuberances on the inner side of the inner ring section, preferably consist of an elastic material, namely polymer material. If the loose flanges themselves are produced from polymer material, then the protuberances and/or clamping noses may simply be integrally formed thereon.
It is also an object of the present invention to specify a method of producing a loose flange for a pipe connection, with the result that a flange body with a clamping-force capacity which is stable over a long period of time is provided in a manner which is straightforward in production terms.
In order to achieve this object, the method according to the invention, in conjunction with the preamble of Patent Claim 18, is characterized in that two identical annular flange parts are formed separately by injection moulding or casting, with a radially inwardly oriented flattened portion being formed in the process, and in that, in a second step, the flange parts are connected to one another in an outer ring section, with a groove produced by the mutually facing flattened portions being formed in the process.
The particular advantage of the method according to the invention is the simplicity of production. Preferably identical flange halves are formed separately and then welded to one another with surface-area abutment of radial surfaces of an outer region section. The flange parts or flange halves are thus of straightforward geometrical shape, with the result that they can be produced with a relatively high throughput.
According to a preferred embodiment of the method according to the invention, the shaped parts are produced from a polymer material by injection moulding, it being possible for the fixed connection between the same to be easily produced by welding.